This invention relates to the field of probes for delivering excitation light to and collecting response light from a target for spectral analysis.
Many materials express light when excited by incident light. The characteristics of expressed light in response to various excitation light wavelengths can identify the material. Different response spectra can also identify different material properties, as for example in cervical cells where precancerous cells have different response spectra than normal cells. See, e.g., Romanujam et al., U.S. Pat. No. 5,421,339.
Some current spectral imaging systems mount with a laboratory microscope. See, e.g., Fluorescence Imaging Spectroscopy, and Microscopy, Wang and Herman editors, 1996, Chapter 5. Laboratory microscope imaging systems add a high power light source, optics, and detection hardware to a conventional laboratory microscope. These systems are well suited for imaging samples suitable for examination on a microscope stage. They can not, however, image large targets, support in situ imaging, or allow imaging in confined spaces. They are also not suitable for use in hostile environments such as under water, in outer space, or in the presence of hazardous gases.
Other current spectral imaging systems mount as part of a large mobile platform. See, e.g., Airborne Visible Hyperspectral Imaging Spectrometer: Optical and System Level Description, in Imaging Spectrometry II, Meigs, Butler, Jones, Otten, Sellar, Rafert, Descour and Mooney editors, SPIE volume 2819 page 278, 1996. These systems are often used for satellite imaging of the earth using sunlight as the excitation light. They can be designed for use in certain hostile environments. They are not capable, however, of high resolution spectral imaging because they do not have control over the distance to the target and do not generate selectable wavelength excitation light. They can image very large targets, but are not capable of precisely imaging areas less than tens of meters at a time. They also are not capable of imaging in confined spaces or of imaging various aspects of a target.
Many materials whose properties are of interest can not be moved. For example, cells attached or within a body must be either biopsied (an invasive procedure) or imaged in situ. Materials embedded in structures such as pipelines must be imaged in situ. Often, materials to be imaged can only be accessed in a confined space. Examples include cervical cells and the interior of enclosed structures. Determining properties of materials located in hazardous environments can pose danger to humans making the determination.
There is therefore a need for a multispectral imaging probe that can deliver a range of wavelengths of excitation light to a target and collect a range of expressed light wavelengths, that is adapted for mobile use and use in confined spaces, and that is sealed against the effects of hostile environments.